Biology subjects

Dozois, C. M.

Publications and source records attributed to Dozois, C. M..

5 recordsLinked to original sources

bioRxiv2026

Amino Sugar Metabolism with AgaSY Coordinates Carbon Catabolism, Fimbrial Regulation, and Pathogenesis in Uropathogenic E. coli

Uropathogenic Escherichia coli (UPEC) exploit alternative carbon sources in order to adapt to the nutrient-limited urinary tract. While glucose is often scarce in healthy human urine, UPEC express a variety of sugar transport and catabolic systems that promote fitness during infection. In this study, we identify the agaSY genes in UPEC strain CFT073 as essential for the catabolism of the amino sugars N-acetyl-galactosamine (GalNAc or Aga) and galactosamine (GalN or Gam) and for the efficient use of additional amino sugars and carbon sources. Deletion of agaSY not only abolished Aga utilization but also impaired catabolism of multiple carbon sources including amino acids and sugars tested using phenotypic arrays. The {Delta}agaSY mutant exhibited significantly reduced type 1 fimbriae production, reduced biofilm formation, and increased motility, suggesting a link between amino sugar metabolism and the regulation of bacterial surface structures. Loss of agaSY did not affect growth and adherence to bladder cells and increased expression of genes encoding F9 fimbriae. Furthermore, the {Delta}agaSY mutant was significantly attenuated for bladder and kidney colonization in a murine urinary tract infection model, while complementation restored urinary tract colonization. The results indicate that a combination of deficiencies in nutrient acquisition, altered carbon metabolism, and regulation of virulence-associated factors contributes to reduced urinary tract colonization. Our findings highlight the interplay between metabolic flexibility and virulence regulation, as well as the central role that amino sugar metabolism plays in UPEC pathogenesis.

microbiology↗

bioRxiv2026

Regulation of PL fimbriae (plf) and role of PlfB as a negative regulator during avian pathogenic Escherichia coli infection in turkeys

Little is currently known about the regulation of PL fimbriae produced by some pathogenic E. coli strains. We identified PlfB, a transcriptional regulator of the PapB family, as a negative regulator of PL fimbriae (Plf). Deletion of plfB significantly increased plfA transcription and Plf production. PlfB bound specifically to the plfA promoter region. Using a PplfA-lux reporter system, the deletion of plfB caused sustained and increased expression across serial passages. Global regulatory genes such as lrp, argR, and hns were also implicated in regulation of plf expression. Loss of lrp or argR decreased plf expression, suggesting these regulators positively regulate PL fimbriae. By contrast, loss of hns increased levels of plf expression, supporting its role as a negative regulator. Interestingly, loss of plfB significantly increased bacterial colonization in the lung of 6-day-old turkey poults. Further, complementation of plfB restored plf fimbrial expression and colonization of turkey lungs to wild-type levels. This further supports an important role for PL fimbriae for colonization of turkey lungs, since loss of plfB which resulted in increased plf gene expression in turkey lungs also correlated with higher bacterial numbers in the lungs. Taken together, these results indicate that PlfB acts as a negative regulator to reduce levels of PL fimbrial expression, under some conditions, but that it is not required for plf expression. This contrasts with the role the PapB regulator, which has been shown to play an essential role in expression of P fimbriae in uropathogenic E. coli strains.

microbiology↗

bioRxiv2025

Host range and zoonotic potential linked to P-like fimbrial adhesin specificity in avian pathogenic Escherichia coli

Fimbrial adhesins are surface-associated bacterial proteins that contribute to colonization, tissue tropism, and biofilm formation. Genomic analysis of the avian pathogenic Escherichia coli (APEC) strain QT598 identified a plasmid-localized fimbrial operon, termed plf which encodes P-like (PL) fimbriae. Herein, we investigated the role of P-like (PL) fimbriae, encoded on the ColV plasmid of APEC strain QT598, in a natural host turkey respiratory infection model. We determined that deletion of the plf genes reduced colonization in the lungs of turkeys. The PlfG class II fimbrial adhesin from APEC strain QT598 demonstrated species- and tissue-specific adherence, as adherence to turkey lung sections in vitro was more pronounced than adherence to chicken lung sections. In vivo, expression of plf was also found to be upregulated in the lungs of turkeys during infection, as determined by qRT-PCR. Glycan array analysis showed that the PlfG class II adhesin recognizes Lewis b, Lewis y, and H antigens as potential receptors that are present on human red blood cells and on the surface of turkey respiratory tissues, implicating specific -1,2-linked glycans as receptors. Structural modelling of Plf adhesin revealed conserved {beta}-sandwich folds with distinct binding pockets that predict receptor specificity differences between Plf adhesin variants and other fimbrial adhesins such as PapG II and the PlfG class I adhesin from UMEA 3703-1. These findings highlight the role of PL fimbriae in APEC virulence and suggest a potential zoonotic and foodborne risk from poultry to humans, demonstrating the common recognition of glycans present on both turkey and mammalian host cells and tissues. Author summaryFimbrial adhesins may play a role in bacterial attachment and colonization of host cells. We examined the role of new pap-like (PL) fimbriae in an Avian Pathogenic E. coli (APEC) strain originally isolated from a systemic infection in a young turkey poult using genetic, molecular, and cell culture methods, as well as a turkey infection model. Deletion of plf genes also decreased colonization in the turkeys lungs, and comparison between the wild-type APEC isolate and the plf-mutant showed that these fimbriae strongly promote adherence to turkey lung sections compared to chicken lung sections. The PL fimbrial adhesin of strain QT598 demonstrated receptor-specificity to fucose [a]-1,2-galactose containing glycans, including Lewis b, Lewis y, and H antigens or similar glycans as determined by carbohydrate inhibition and glycan array experiments. These findings highlight the role of PL fimbriae in APEC virulence and suggest a potential zoonotic and foodborne risk from poultry to humans, demonstrating the common recognition of glycans present on both turkey and mammalian host cells and tissues.

microbiology↗

bioRxiv2022

Adaptive radioresistance of Enterohemorrhagic Escherichia coli O157:H7 results in genomic loss of shiga toxin-encoding prophages

Enterohemorragic Escherichia coli (EHEC) O157:H7 is a foodborne pathogen producing shiga toxins (Stx1 and Stx2), can cause hemorrhagic diarrhea, and life-threatening infections. O157:H7 strain EDL933 carries prophages CP-933V and BP-933W that encode shiga toxin genes (stx1 and stx2 respectively). The aim of this work was to investigate the mechanisms of adaptive resistance of EHEC strain EDL933 to a typically "lethal" dose of {gamma}-irradiation (1.5 kGy). Adaptive selection through six passages of exposure to 1.5 kGy resulted in the loss of CP-933V and BP-933W prophages from the genome and mutations within three genes: wrbA, rpoA, and Wt_02639 (molY). Three selected EHEC clones that became irradiation-adapted to the 1.5 kGy dose (C1, C2 and C3) demonstrated increased resistance to oxidative stress, sensitivity to acid pH, and decreased cytotoxicity to Vero cells. To confirm that loss of prophages plays a role in increased radioresistance, C1 and C2 clones were exposed to bacteriophage containing lysates. Although, phage BP-933W could lysogenize C1, C2, and E.coli K-12 strain MG1655, it was not found to have integrated into the bacterial chromosome in C1-{Phi} and C2-{Phi} lysogens. Interestingly, for the E. coli K-12 lysogen (K12-{Phi}), BP-933W DNA had integrated at the wrbA gene (K12-{Phi}). Both C1-{Phi} and C2-{Phi} lysogens regained sensitivity to oxidative stress, were more effectively killed by a 1.5 kGy {gamma}-irradiation dose and had regained cytotoxicity and acid resistance phenotypes. Further, the K12-{Phi} lysogen became cytotoxic, more sensitive to {gamma}-irradiation and oxidative stress and slightly more acid resistant. ImportanceGamma ({gamma})-irradiation of food products can provide an effective means of eliminating bacterial pathogens such as enterohemorrhagic Escherichia coli (EHEC) O157:H7, a significant foodborne pathogen that can cause severe disease due to the production of Shiga toxins. To decipher the mechanisms of adaptive resistance of the O157:H7 strain EDL933, we evolved clones of this bacterium resistant to a lethal dose of {gamma}-irradiation by repeatedly exposing bacterial cells to irradiation following a growth restoration over six successive passages. Our findings provide evidence that adaptive selection involved modifications in the bacterial genome including deletion of the CP-933V and BP-933W prophages. These mutations in EHAC O157:H7 resulted in loss of stx1, stx2, loss of cytotoxicity to epithelial cells and decreased resistance to acidity, critical virulence determinants of EHEC, concomitant with increased resistance to lethal irradiation and oxidative stress. These findings demonstrate that the potential adaptation of EHEC to high doses of radiation would involve elimination of the Stx encoding phages and likely lead to a substantial attenuation of virulence.

microbiology↗

bioRxiv2021

A newly identified group of P-like (PL) fimbriae from extra-intestinal pathogenic Escherichia coli (ExPEC) encode distinct adhesin subunits and mediate adherence to host cells

Fimbrial adhesins play a critical role for bacterial adherence and biofilm formation. Sequencing of avian pathogenic Escherichia coli (APEC) strain QT598 identified a fimbrial gene cluster belonging to the {pi} group that we named PL (P-like) fimbriae, since genetic organization and sequence are similar to Pap and related fimbriae. Screening of genomic databases indicated that genes encoding PL fimbriae located on IncF plasmids are present in a diversity of E. coli isolates from poultry, human systemic infections, and other sources. As with P fimbriae, PL fimbriae exhibit sequence divergence in adhesin encoding genes, and strains could be divided into 5 classes based on differences in sequences of the PlfG adhesin protein. The plf genes from two predominant PlfG adhesin classes, PlfG-I and PlfG-II were cloned. PL fimbriae were visualized by electron microscopy, promoted biofilm formation, demonstrated distinct hemagglutination profiles and promoted adherence to human bladder and kidney epithelial cell lines. Hybrid fimbriae comprised of genes from plfQT598 wherein plfG was replaced by papG encoding adhesin genes were also shown to be functional and mediate adherence to epithelial cells, further indicating similarity and functional compatibility between these two types of fimbriae. Although deletion of plf genes did not significantly reduce colonization of the mouse urinary tract, plf gene expression was increased over 40-fold in the bladder compared to during in vitro culture. Overall, PL fimbriae represent a new group of fimbriae demonstrating both functional differences and similarities to P fimbriae and may contribute to adherence to cells and colonization of host tissues. ImportanceFimbriae are important colonization factors in many bacterial species. The identification of a new type of fimbriae encoded on some IncF plasmids in E. coli was investigated. Genomic sequences demonstrated these fimbrial gene clusters have genetic diversity, particularly in the adhesin encoding PlfG gene. Functional studies demonstrated differences in hemagglutination specificity, although both types of Plf adhesin under study mediated adherence to human urinary epithelial cells. Such fimbriae may represent previously unrecognized adhesins that could contribute to host specificity and tissue tropism of some E. coli strains.

microbiology↗